Shear stress-resistant systems, such as those that display anisotropic resistance to applied forces are particularly useful in applications that require freedom of movement in a desired direction, but not in other directions. These systems allow for repeated strong attachment and facile detachment of objects depending on the direction of the applied force. An example of such a system is found in nature in the foot pads of insects and the wall-climbing gecko. See, e.g., Yao, et al., “Adhesion and sliding response of a biologically inspired fibrillar surface: experimental observations,” J. R. Soc. Interface, 5:723-733 (2008); Ge, et al., “Carbon nanotube-based synthetic gecko tapes,” Proc. Nat. Acad. Sci., 104(26): 10792-10795 (2007); Jin, et al., “Challenges and solutions for joining polymer materials,” Macromol. Rapid Commun., 35:1551-1570 (2014).
Ge et al., describe carbon nanotube-based synthetic tapes that display anisotropic properties that are similar to those displayed on the foot pads of a gecko, but show shearing resistance four times higher than the gecko's foot pads. However, these synthetic tapes are non-specific and bind to almost any surface. See Jin, et al. Systems and materials that exhibit such non-specific binding can require protective release liners during shipment, to prevent the materials (e.g., synthetic tapes) from attaching to unintended surfaces or from picking up impurities.
Also, the use of a release liner increases the expense and negative environmental impact with respect to production and elimination of waste.
Accordingly, there remains a need for improved removable, and optionally re-attachable systems and materials.
Therefore, it is an object of the invention to provide improved attachment systems and materials.
It is also an object of the invention to provide methods of making and using such systems and materials.